Hello Jason,
please have a look into the L4 Version X.2 Reference Manual Section 2.4 available here http://os.ibds.kit.edu/l4ka/l4-x2-r7.pdf - no code there though. You may consider asking further questions on the l4ka mailing https://lists.ira.uni-karlsruhe.de/pipermail/l4ka/. Chances are high that you meet the Pistachio hackers there.
From my last look into the Pistachio sources I remember a tiny test
program user/apps/l4test that (among other tests) creates threads.
Greets